Concepts inQuery ranking in probabilistic XML data

XML

{{stack| {{Infobox file format | icon = | logo = | screenshot = | extension = . xml | mime = application/xml, (deprecated in an expired draft) and end with a, or begin with the character and end with a . Strings of characters which are not markup are content. Tag A markup construct that begins with and ends with .
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Tuple

In mathematics and computer science, a tuple is an ordered list of elements. In set theory, an (ordered) -tuple is a sequence (or ordered list) of elements, where is a positive integer. There is also one 0-tuple, an empty sequence. An -tuple is defined inductively using the construction of an ordered pair. Tuples are usually written by listing the elements within parentheses "" and separated by commas; for example, denotes a 5-tuple.
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Dynamic programming

In mathematics and computer science, dynamic programming is a method for solving complex problems by breaking them down into simpler subproblems. It is applicable to problems exhibiting the properties of overlapping subproblems which are only slightly smaller and optimal substructure (described below). When applicable, the method takes far less time than naive methods. The key idea behind dynamic programming is quite simple.
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XPath

XPath, the XML Path Language, is a query language for selecting nodes from an XML document. In addition, XPath may be used to compute values from the content of an XML document. XPath was defined by the World Wide Web Consortium (W3C) .
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Probability

Probability is ordinarily used to describe an attitude of mind towards some proposition of whose truth we are not certain. The proposition of interest is usually of the form "Will a specific event occur?" The attitude of mind is of the form "How certain are we that the event will occur?" The certainty we adopt can be described in terms of a numerical measure and this number, between 0 and 1, we call probability.
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Possible world

In philosophy and logic, the concept of a possible world is used to express modal claims. The concept of possible worlds is common in contemporary philosophical discourse and has also been disputed.
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